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Influence of ionts on the efficiency of shrinkage reducing admixtures in alkali activated systems
Vašíčková, Kateřina ; Bílek, Vlastimil (referee) ; Kalina, Lukáš (advisor)
Alkali activated materials, especially when activated with waterglass, are subjected to substantial drying shrinkage that hinders their broader industrial application. The effect of shrinkage reducing admixtures (SRA), based on poly(propylene glycol), on drying shrinkage of alkali activated blast furnace slag (BFS) mortars was studied. The aim of this thesis is to determine the efficiency of SRA as well as the influence of different type of alkali activator with varying silicate modulus on drying shrinkage characteristics. It was observed that the high amount of alkalis positively influenced the effect of SRA. The higher the amount of alkalis, the lower the drying shrinkage was. It also caused more water to be incorporated in the alkali activated structure and prevent it from evaporation. Thus, the weight change of such mortars was the lowest. Reduced effect of SRA on mechanical strength properties was observed in mortars with low amount of alkalis which was connected with delayed hydration resulting in insufficient amount of created C-S-H gel. The presented thesis further discussed and underlines the role of different kinds of alkali ions as well as their amount on the properties of alkali activated BFS systems.
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Effect of curing conditions on shrinkage of alkali activated systems
Pragerová, Barbora ; Kotrla, Jan (referee) ; Kalina, Lukáš (advisor)
This bachelor thesis deals with the determination of optimal curing conditions of alkali-activated systems in order to reduce shrinkage. Hardened alkali-activated blast-furnace slag pastes activated by sodium silicate were tested in the empirical part. Six varieties of curing conditions were compared. Immediately after demolding process, three sets of samples were stored in air, water and plastic film. Another three sets were first placed in water for 14 days, then removed and two of them impregnate with lithium silicate and acrylate-based coatings. The formation and the number of cracks were monitored by an optical method. The percentage of cracks was evaluated by the ImageJ program. The highest number of cracks was formed after 7 days of curing, given the samples placed in the open air. Some them were filled later. Samples placed in the open air after being submerged in water for 14 days showed a rapid increase of cracks as well, but the percentage of cracks was reduced to 50 %. Treating agents reduced the development of cracks but have not stopped their formation. After 36 days of curing, the results of these types of curing conditions were comparable. Only the samples wrapped in plastic foil showed a minimum number of cracks and no cracks were observed if the samples were submerged in water. The lowest levels of shrinkage were reached with the samples placed in water, and with the ones wrapped in plastic foil. Samples stored in water for the first 14 days showed the identical tendency of high-level shrinkage, as did the ones placed in the open air.
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Utilization of lignosulfonate plasticizer in alkali-activated materials
Zetocha, Martin ; Hrubý, Petr (referee) ; Kalina, Lukáš (advisor)
Tato bakalářská práce se zabývá využitím plastifikátorů na bázi lignosulfonátu v alkalicky aktivovaných materiálech. Sledován byl vliv na směs pasty aktivované vysokopecní strusky za použití hydroxidu sodného, vodního skla o různých modulech a uhličitanu sodného. Pozorován byl vliv plastifikátoru na bázi lignosulfonátu při zamíchávání do různých směsí, na zpracovatelnost, mechanické vlastnosti a reologii směsi. Důležitým faktorem byly použité aktivátory ve směsích. Nejlépe reagující směs na lignosulfonát se ukázala být za použití NaOH jako aktivátoru. Při pokusech pochopit reologické vlastnosti sledovaných směsí, jako klíčového faktoru chování těchto směsí bylo měření zeta potenciálu. Hodnoty zeta potenciálu nám daly bližší náhled na povrchový náboj častic vysokopecní strusky. Ten se prokázal jako klíčový faktor při posuzovaní účinnosti plastifikátoru. Tato zjištění budou vzata v úvahu a dále diskutovány v této práci.
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Study of the influence of compositon on the mechanical properties of high performance concrete
Veleba, Ondřej ; Šoukal, František (referee) ; Krátký, Josef (advisor)
This work is devoted to study the influence of the composition on mechanical properties of high performance concret based on portland cement. 29 samples of high performance concrete (HPC) warying in composition were prepared. The constituents used for HPC preparation were: cement Aalborg White, silica fume, finelly ground blast furnace slag, finelly ground silica, calcinated bauxite and polycarboxylate based superplasticizer. The mechanical parameters (flexural and compressive strength) of the samples were observed after 7 and 28 days of moist curing. Compressive strength values after 28 days were in the range of 92 to 194 MPa and the flexural strength values were in the range of 7 to 23 MPa (without using of fiber reinforcement). The graphs showing mechanical parameters depending on the mixture composition were constructed and consequently evaluated.
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Reduction of efflorescence in the geopolymer systems
Suchý, Rostislav ; Šoukal, František (referee) ; Kalina, Lukáš (advisor)
Alkali metal cations are weakly bound in the structure of alkali activated materials. This fact causes the formation of undesirable efflorescence in humid environment. In this work, the effect of fluoride additives, which significantly reduce the efflorescence, was investigated. The chemical mechanism of selected additive in the modified binder was studied based on XRD, SEM EDX and ICP OES analysis. Also the effect of the added fluorides on the mechanical properties of the final product was monitored.
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On the mechanisms of shrinkage reducing admixtures in alkali activated materials
Komosná, Kateřina ; Bartoníčková, Eva (referee) ; Kalina, Lukáš (advisor)
This thesis is focused on the principles of behavior of shrinkage reducing agents (SRA) in alkali-activated materials based on blast furnace slag. The main focus of this work is selecting the most suitable admixture based on experiments, by which will be achieved through minimal shrinkage and will have negative effect on the properties of alkali-activated blast furnace slag at the same time. In experimental section of this work, the surface tension as individual additives as their mixtures with pore solution were measured primarily. Then the testing samples composed of blast furnace slag, water glass and addition of SRA were prepared. Of these samples was measured shrinkage and weight loss. Moreover, their mechanical properties such as flexural and compressive strength were monitored. Next, the beginning and the end of solidification was studied using the Vicat device and last but not least workability. The hydration process of alkali-activated materials with SRA was measured calorimetrically. Finally the microstructure in prepared samples was observed using scanning electron microscopy (SEM-EDS) and the total porosity was determined by mercury porosimeter.
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The leachability of metals from geopolymers using various leaching mediums
Bystrianska, Emília ; Beranová, Denisa (referee) ; Koplík, Jan (advisor)
The aim of this work is the comparison of the leachability of metal from AAM due to the use of various leaching mediums. The ability to stabilize 1 wt. % Pb2+ in alkali-activated matrices was compared using different leaching tests (ČSN EN 12457, HJ-T/299, TCLP). The concentration of metal content in leachate was determined by ICP-OES method. The matrices consisted of blast-furnace slag and high-temperature fly ash. Lead distribution in matrices was analyzed by SEM microscopy. Furthermore, the effect of mechanical strength and pH leachate on the lead concentration were examined.
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Comparision of leachability of heavy metals from various types of alkali-activated alumino-silicate systems
Smolková, Miroslava ; Kalina, Lukáš (referee) ; Koplík, Jan (advisor)
The work deals with the determination and comparison of leaching of heavy metals from various types of alkali-activated alumino-silicate systems (high-temperature fly ash, blast furnace slag). Such alkali activated materials are capable in their structure effectively encapsulate heavy metals, toxic chemicals or other contaminants, which can be beneficial for the environment. The aim of this work is to obtain a mixture with acceptable mechanical properties that could be useful for the inhibition of these substances. Leachability was tested according to norm ČSN EN - 12457-4, followed by analysis by ICP-OES. The structure of the matrix was investigated using SEM equipped with EDS.
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Development of high-strength concrete defined properties with the use of secondary raw materials
Ondráček, Michal ; Vítek,, Jan (referee) ; Ďurica,, Tibor (referee) ; Vymazal, Tomáš (referee) ; Hela, Rudolf (advisor)
Civil engineering development is connected with the application of new construction methods and the development of new building materials. Concrete, as one of the basic building materials, is part of this development. A major turning point in the development of concrete and its properties occurred with the use of new, more efficient plasticizing additives. This allowed to produce concrete with lower water cement ratio, while increasing the strength of concrete. Gradually, the compressive strength of concrete boundary has moved by several levels, when there are currently commonly used concrete with strength of about 100 N/mm2 and with the special methods of concrete production strength range from 250 to 300 N/mm2. A negative aspect of the development of (ultra) high-strength concrete is their energy and economic demands. A characteristic feature of high-strength concrete is a high content of cement and very fine admixtures, especially silica fume. One way to improve the economics of these types of concrete is the application of cheaper admixture based on industrial waste. The content of this work is the observation and description of the properties of high-strength concrete and reactive powder concrete, in which the admixtures were based on industrial waste were applied. Part of this work is the comparison of economic parameters for individual types of concrete.
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